. The human body and health : an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools . irs, join thespinal cord. Some of the nerves are for the purpose oftransmitting orders from the central nervous system tothe muscles, and are therefore called motor nerves. Thesensor^/ nerves carry messages from various parts of the CRANIAL NERVES body to the spinal cord andbrain. The nerve leadingfrom the retina of the eyeis a sensory nerve, whilethe nerve extending fromthe brain to the musclesto move the eye is amotor nerve. Frequentlymotor and sensory fibersare
. The human body and health : an elementary text-book of essential anatomy, applied physiology and practical hygiene for schools . irs, join thespinal cord. Some of the nerves are for the purpose oftransmitting orders from the central nervous system tothe muscles, and are therefore called motor nerves. Thesensor^/ nerves carry messages from various parts of the CRANIAL NERVES body to the spinal cord andbrain. The nerve leadingfrom the retina of the eyeis a sensory nerve, whilethe nerve extending fromthe brain to the musclesto move the eye is amotor nerve. Frequentlymotor and sensory fibersare bound together in thesame nerve, as is the casein all those nerves con-nected with the spinalcord. Cranial Nerves. — All ofthe twelve pairs of cranialnerves, with the exceptionof one pair, supply thehead, neck, or upper partof the shoulders. Theyare numbered from beforebackward according to theorder in which they arejoined to the brain. Theyare also named accordingto their function or in ac-cordance with the regionwhich they supply. Thefirst pair of cranial nervesare the olfactory^ or nervesof smell, and the second^ or 221. Fig. 150. — View from the side of partof tlie sympattietic nervous systemwitliin the body cavity. The whitelines are nerves, a, spinal nerves tothe arm; 72,lieart; i, intestines; n,ganglia, or bunches of cell bodies onthe sympathetic nerve cord ; p, one ofthe four large plexuses of the sym-pathetic system ; t, stomach ; 10, tenthcranial nerve to lungs and stomach. 222 HOW THE NERVOUS SYSTEM IS CONSTRUCTED optie^ are the nerves of sight. The eighth pair are themiditory nerves^ leading from the ear. Spinal Nerves. — All the 31 pairs of spinal nervescontain both motor and sensory fibers. Each nerve isunited to the cord by two branches, named roots^ the backone of which is the dorsal root^ and the front one is theventral root. If the dorsal root of a spinal nerve is cut,the part of the body supplied by the nerve is withoutfeeling, while if the other root i
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